It's tough to calculate the number of people sporting the sweaters and attending ugly sweater-themed parties, but turn to TipsyElves.com, and you'll see the popularity is growing. In just one year, the site's web traffic has doubled.

"We see it as a growing trend that we think is going to be here to stay for quite some time," said Evan Mendelsohn, who co-founded TipsyElves.com. "We'd like it to be the next Halloween, which it almost seems like it's becoming."

At World Thrift in Lake Worth, Florida, employees told us they're amazed by how many people donate their holiday sweaters year-round. They're even more shocked by how fast the sweaters resell.

"We put out 15 yesterday, and they're all gone," said assistant manager Italo Calderon. "We only have one left."

And Coke Zero now has a Sweater Generator that lets you decorate your own online, then submit it for votes. The winning entries will be made into actual sweaters.

This year, the Christmastime craze has grown beyond just sweaters though. You can find sweater dresses, which allow for a more flattering fit for women, or even matching jumpsuits for couples. As you zip this one up, the reindeer on each side appear to kiss.

"People are having onesie parties, so to us, it was really a perfect fusion of the onesie trend with the Christmas sweater trend," Mendelsohn said.

And something that'll warm your heart this year, besides a sweater? Knowing that you can give back to a cause with your hideous holiday purchase.